1. Field of the Invention
This invention relates in general to cable-type hoisting and traction apparatus in which the cable is driven as a consequence of its adherence to a pulley, which results from means pressing this cable against the walls of the groove.
2. Description of the Prior Art
In known apparatus of this character, this driving pressure is provided either by spring means, and in this case the pressure has a fixed value irrespective of the load, or preferably by one or more rollers coupled to a lever mechanism responsive to the position of a deflection pulley engaging the taut cable section tensioned by the load.
In this last case, and for this purpose, the deflection pulley is pressed against the cable tensioned by the load so that a component of this load, applied to the taut cable section, exerts on this deflection pulley an action causing the lever mechanism to press the roller or the set of rollers against the cable, thus providing the desired adherence of this cable to the bottom of the groove of the driving pulley.
However, this know arrangement is objectionable in that it requires the use of a deflecting pulley arranged according to couplings other than the kinematic connections transmitting the drive from the power unit to the load. Now this pulley not only constitutes an additional component element of which the over-all dimensions are incremented, in certain cases, by the necessity of meeting certain safety rules, but exerts on the cable a wearing action not partaking in the driving action. Finally, the safety of operation of the driving system is dependent upon the proper cooperation between the deflection pulley and the taut end of the cable.